Tick-Borne Disease Infections and Chronic Musculoskeletal Pain

This cross-sectional study examines the prevalence of spotted fever group rickettsiosis, ehrlichiosis, and α-gal syndrome and their association with symptomatic radiographic knee osteoarthritis in adults 45 years or older.


eMethods. Details on multivariable models
Multivariable models were used to assess the independent association of TBD seroprevalence with hand, hip, and knee joint PAS severity count and symptomatic rKOA.These models were adjusted for age, sex, race, BMI, education, smoking, alcohol use, Charlson comorbidity index.The dichotomous outcome of symptomatic rKOA was modeled using logistic regression to produce adjusted OR and 95% CI for positive Ehrlichia IgG, positive Rickettsia IgG and alpha-gal IgE > 0.1 IU/mL with symptomatic rKOA.The score count outcomes of severity PAS for hands, hips, and knees were each modeled using Zero-inflated negative binomial distribution to produce adjusted mean ratios (MR) and 95% CI to quantify the association of positive Ehrlichia IgG, positive Rickettsia IgG and Alpha-gal IgE > 0.1 IU/mL with PAS joint severity.The log of the mean PAS severity count is being modeled and the MR can be interpreted as how much worse the joint PAS severity is on average between two groups, for example how much worse the hand PAS severity is on average for participants with positive Ehrlichia IgG compared to participants negative.All of these sets of multivariable models were repeated replacing the dichotomous covariable Alpha-gal IgE > 0.1 IU/mL with a four-level variable: Alpha-gal IgE=0 IU/mL (reference), 0 IU/mL<Alphagal IgE≤0.1 IU/mL, 0.1 IU/mL<Alpha-gal IgE≤0.35IU/mL, and 0.35 IU/mL<Alpha-gal IgE.
Multivariable models were used to assess the independent association of seroprevalence with the KOOS subscale scores.These models were adjusted for age, sex, race, BMI, education, smoking, alcohol use, Charlson comorbidity index.The score outcomes KOOS subscale were each modeled using Zero-inflated negative binomial distribution to produce adjusted MR and 95% CI to quantify the association of positive Ehrlichia IgG, positive Rickettsia IgG and Alpha-gal IgE > 0.1 IU/mL with KOOS subscale severity.The log of the mean KOOS subscale score is being modeled and the MR can be interpreted as how much worse the KOOS subscale score is on average between two groups, for example how much worse the KOOS Pain subscale score is on average for participants with positive Ehrlichia IgG compared to participants negative.To account for excess number of scores equal to 100, KOOS subscale scores were reversed as 100 minus score so the higher the score the worse the knee assessment.This allowed the fit of a zero-inflated model that can account for the excess zeros (in this case, corresponding to excess 100 scores).
DL et al.JAMA Network Open

Multivariable models for symptomatic radiographic osteoarthritis as well as Hands, Hips and Knees PAS
Unless otherwise indicated, data are expressed as No. (%) of participants.Percentages have been rounded and may not total to 100.Elevated blood pressure defined by systolic blood pressure >140mm Hg or diastolic blood pressure >90mm Hg.Abbreviations: MR, mean ratio; CI, confidence interval; PAS, pain, aching, stiffness; rKOA, radiographic knee osteoarthritis.Models adjusted by age, BMI, sex, race, education, smoking status, alcohol use, Charlson comorbidity index, and other listed covariates.The first set of models, by outcome, include the covariables listed in the first three rows; the remaining models include the covariables in the latter rows.
eTable 1. Alpha-gal and Total IgE levels.Distribution of alpha-gal IgE levels among 488 participants.Abbreviations: BMI, body mass index; HS, high school; CKD, chronic kidney disease.a : b :